The present invention relates to a transfer sheet suitable for the formation, with high precision and ease, of electrode patterns, dielectric layers, barrier layers, etc. for use with plasma display panels (PDPs), field emission displays (FEDs), liquid crystal displays (LCDs), fluorescent displays, hybrid integrated circuits, etc.
For fine patterns such as electrodes, dielectric layers, barrier layers, etc. for use with PDPs, it is now required that they be fabricated at low fabrication costs while thickness accuracy and pattern accuracy are maintained at high levels.
So far, patterns for use with PDPs have been provided by forming a patterning paste having desired properties into a given pattern by a printing process such as screen or offset printing, followed by drying, and firing. This printing process involves simple steps, and so is expected to lead to production cost reductions. However, problems with the screen printing process are that the elongation of a mesh material forming a screen printing plate places some limitation on printing accuracy, and that the edge accuracy of the resultant pattern becomes low due to the occurrence of meshes in the pattern or the spreading of the pattern. A problem with the offset printing process is, on the other hand, that thickness accuracy and pattern accuracy decrease with increasing printing cycles because some patterning paste is not perfectly transferred to a substrate and so remains on a blanket. It is consequently required to make frequent blanket replacements, thereby preventing the paste from remaining on the blanket and maintaining the accuracy of the pattern upon forming. The operation to this end is, however, very troublesome.
A given thick-film pattern having a high aspect ratio, e.g., a PDP barrier pattern, has so far been formed by a screen printing process. With the screen printing process, the limitation of film thickness formed in one single cycle is of the order of a few tens xcexcm. In other words, printing and drying cycles should be repeated many times, generally 10 or more times. A coating film formed by the screen printing process is generally of a convex shape in section or is bulging out. Consequently, when a multiplicity of printing cycles are carried out as mentioned above, coating solution sags are built up at the periphery of the pattern, and so make the pattern have a spreading bottom.
It has recently been proposed to form a barrier layer using a transfer sheet comprising a glass paste provided on a base film (JP-A 8-273536). This process makes use of the transfer sheet having a glass paste layer, and is advantageous in that the process of fabricating barriers for PDP panels can be simplified. However, problems arise in connection with the trapping of air bubbles by transfer, and the releasability of the glass paste layer from the base film. Especially when a fine electrode pattern or dielectric layer is formed by use of the transfer sheet, air bubbles, etc. are likely to pass into the transfer layer. Also, poor transfer causes breaks in the electrode pattern or pinholes in the dielectric layer.
In view of such problems as mentioned above, one object of the invention is to provide a transfer sheet which can be used to form, with great accuracy, fine patterns such as electrodes, resistors, e.g., dielectric layers, barriers, etc. for use image displays such as PDPs and LCDs, thermal heads, integrated circuits, etc.
Another object of the invention is to provide a transfer sheet which can be used to form, with great accuracy, primer layers, dielectric layers on front and back panels, photosensitive black matrix layers, and photosensitive rib layers for use with PDPs in particular.
Yet another object of the invention is to provide a transfer sheet which makes it possible to form a high-definition electrode pattern.
According to the first aspect of the invention, there is provided a transfer sheet comprising, at least, a base film and a transfer layer releasably provided on the base film, characterized in that the transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and has a surface roughness Ra of at most 0.4 xcexcm.
Preferably, the transfer layer is characterized by having a releasable protective film thereon, and in that the surface roughness Ra of the transfer layer upon the protective film released therefrom is at most 0.2 xcexcm.
Preferably, the organic component is characterized by being sensitive to light.
Preferably, the transfer layer contains a conductive powder as the inorganic component.
The first transfer sheet of the invention comprises, at least, a base film and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing and has a surface roughness Ra of at most 0.4 xcexcm (the surface roughness Ra of the transfer layer upon release of a protective film is at most 0.2 xcexcm). Thus, the transfer layer is improved in terms of surface smoothness; that is, it is substantially free of defects such as agglomerates, pinholes, etc. due to poor dispersion of the inorganic component. When the transfer layer has a protective film thereon, air bubbles are unlikely to be trapped between the transfer layer and the protective film, so that the surface smoothness of the transfer layer can be kept in good condition with an improvement in the transferability of the transfer layer to an associated application member. It is thus possible to form a primer or dielectric layer of uniform thickness. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so improved that high-definition patterns for electrodes, dielectric layers, etc., and high-definition thick-film patterns for barriers, etc. can be formed.
A second transfer sheet of the invention comprises, at least, a base film and a transfer layer releasably provided on the base film, and is characterized in that the transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and has a surface gloss of 20 to 110.
Preferably, the transfer layer is characterized by having a releasable protective film thereon, and in that the surface gloss of the transfer layer upon release of the protective film therefrom is in a range of 30 to 110.
Preferably, the organic component is characterized by being sensitive to light.
The second transfer sheet of the invention comprises, at last, a base film and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component containing glass frit and an organic component removable by firing, and has a surface gloss of 20 to 110 (the surface gloss of the transfer layer upon release of a protective film therefrom is in a range of 30 to 110). Thus, the transfer layer is improved in terms of surface smoothness; that is, it is substantially free of defects such as agglomerates, pinholes, etc. due to poor dispersion of the inorganic component. When the transfer layer has a protective film thereon, air bubbles are unlikely to be trapped between the transfer layer and the protective film, so that the surface smoothness of the transfer layer can be kept in good condition with an improvement in the transferability of the transfer layer to an associated application member. It is thus possible to form a primer or dielectric layer of uniform thickness. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so improved that high-definition patterns for electrodes, dielectric layers, etc., and high-definition thick-film patterns for barriers, etc. can be formed.
A third transfer sheet of the invention comprises, at least, a base film and a transfer sheet releasably provided on the base film, and is characterized in that the transfer sheet comprises, at least, an inorganic component including a glass frit and an electrically conductive powder, and an organic component removable by firing, and has a surface gloss of 20 to 110.
Preferably, the transfer layer is characterized by having a releasable protective film thereon, and in that the surface gloss of the transfer layer upon release of the protective film therefrom is in a range of 40 to 110.
Preferably, the organic component is characterized by being sensitive to light.
The third transfer sheet of the invention comprises a base film, and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component including a glass frit and an electrically conductive powder and an organic component removable by firing, and has a surface glossiness of 20 to 110. Thus, the transfer layer is improved in terms of surface smoothness; that is, it is substantially free of defects such as agglomerates, pinholes, etc. due to poor dispersion of the inorganic component. When the transfer layer has a protective film thereon, air bubbles are unlikely to be trapped between the transfer layer and the protective layer, so that the surface smoothness of the transfer layer can be kept in good condition with an improvement in the transferability of the transfer layer to an associated application member. It is thus possible to form a primer or dielectric layer of uniform thickness. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so improved that high-definition patterns for electrodes, dielectric layers, etc., and high-definition thick-film patterns for barriers, etc. can be formed.
A fourth transfer sheet of the invention comprises, at least, a base film and a transfer layer releasably provided on the base film, and is characterized in that the transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and a peel strength between the base film and the transfer layer is in a range of 2 to 30 g/25 mm.
Preferably, the transfer layer is characterized by having a releasable protective film thereon, and that a peel strength between the protective film and the transfer layer is in a range of 1 to 27 g/25 mm and smaller than the peel strength between the base film and the transfer layer.
Preferably, the organic component is characterized by being sensitive to light.
The fourth transfer sheet, designed for the fabrication of a plasma display panel, comprises a base film and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and has a peel strength in the range of 2 to 30 g/25 mm. Thus, it is possible to transfer, with an improved transferability, the transfer layer to an associated application member because the transfer layer can be released from the base film with no cohesive failure of the transfer layer. When the protective film is provided on the transfer layer while the peel strength between them is in the range of 1 to 27 g/25 mm and smaller than that between the base film and the transfer layer, the protective film can be released from the transfer layer with no cohesive failure of the transfer layer and with no release of the transfer layer from the base film. The release of the transfer layer from the base film, and the release of the protective film from the transfer layer can be mechanically carried out in a stable manner without any large tension variation because the peel strengths are within the aforesaid ranges, so that the transfer layer can be transferred, with great transferability, to the associated application member, thereby forming a dielectric layer of uniform thickness. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so high that a high-definition dielectric pattern can be formed.
A fifth transfer sheet of the invention comprises a base film and a transfer layer releasably provided on the base film, and is characterized in that the transfer layer comprises, at least, an inorganic component including a glass frit and an electrically conductive powder, and an organic component removable by firing, and a peel strength between the base film and the transfer layer is in a range of 0.2 g/25 mm to 30 g/25 mm inclusive.
Preferably, the transfer film is characterized by having a releasable protective film thereon, and in that a peel strength between the protective film and the transfer layer is in a range of 0.1 g/25 mm to less than 30 g/25 mm and smaller than that between the base film and the transfer layer.
Preferably, the organic component is characterized by being sensitive to light.
The fifth transfer sheet of the invention comprises a base film and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component including a glass frit and an electrically conductive powder, and an organic component removable by firing, and has a peel strength in the range of 0.2 g/25 mm to 30 g/25 mm inclusive. Thus, it is possible to transfer, with an improved transferability, the transfer layer to an associated application member because the transfer layer can be released from the base film with no cohesive failure of the transfer layer. When the protective film is provided on the transfer layer while the peel strength between them is in the range of 0.1 g/25 mm to less than 30 g/25 mm and smaller than that between the base film and the transfer layer, the protective film can be released from the transfer layer with no cohesive failure of the transfer layer and with no release of the transfer layer from the base film. The release of the transfer layer from the base film, and the release of the protective film from the transfer layer can be mechanically carried out in a stable manner without any large tension variation because the peel strengths are within the aforesaid ranges, so that the transfer layer can be transferred, with great transferability, to the associated application member, thereby forming a dielectric layer of uniform thickness. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so high that a high-definition dielectric pattern can be formed.
A sixth transfer sheet of the invention comprises, at least, a base film and a transfer layer releasably provided on the base film, and is characterized in that the transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and has a residual solvent content of at most 100 mg/m2.
Preferably, the transfer layer is characterized by having a releasable protective film thereon.
Preferably, the organic component is characterized by being sensitive to light.
Preferably, the transfer layer is characterized by containing an electrically conductive power as the inorganic component.
The sixth transfer sheet of the invention comprises a base film and a transfer layer releasably provided on the base film, which transfer layer comprises, at least, an inorganic component including a glass frit and an organic component removable by firing, and has a residual solvent content of at most 100 mg/m2. Thus, the transfer layer is unlikely to break down by cohesion, and improved in terms of storage stability, and transferability with respect to the base film upon transfer. When the protective film is provided on the transfer layer, it can be well released from the transfer layer. When the organic component is sensitive to light, the accuracy of patterning by exposure and development is so high that high-definition patterns for electrodes, dielectric layers, etc., and high-definition thick-film patterns for barriers, etc. can be formed.